Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$177.36	13.507%	$201.316	$201.32	$201.30	$201.30
Purchase #2	$159.25	13.852%	$181.3093	$181.31	$181.30	$181.30
Purchase #3	$165.53	3.467%	$171.2689	$171.27	$171.25	$171.30
Purchase #4	$57.39	7.166%	$61.5026	$61.50	$61.50	$61.50
Purchase #5	$101.77	7.654%	$109.5595	$109.56	$109.55	$109.60
Purchase #6	$61.52	12.283%	$69.0765	$69.08	$69.10	$69.10
Purchase #7	$162.61	10.609%	$179.8613	$179.86	$179.85	$179.90
7 purchase totals =	$885.43		$973.8941	$973.90	$973.85	$974.00